1. Field of the Invention
The present invention relates to a method of indicating a shift operation for a manual transmission gear, and more particularly, to a method which senses a state of the vehicle operation (including the engine operation) requiring a shift operation for the transmission gear and indicates the necessity of the shift operation for the transmission gear.
2. Description of Background Information
By suitably selecting the gear position of a manual transmission gear of a vehicle in accordance with a parameter of the vehicle operation such as the load applied to the vehicle, the fuel consumption in a preselected running mode of the vehicle, as well as in the actual running condition after the vehicle is brought into the market, can be improved. Conventionally, various methods for indicating a desirable gear position have been proposed. For example, Japanese patent application Laid Open Number 55-31671 discloses a method in which the rotational speed of the engine and the throttle position are monitored, and the vehicle operation requiring an up-shift operation or a down-shift operation is indicated according to the monitored rotational speed of the engine and the throttle position. Japanese patent application Laid Open No. 56-163929 discloses a method in which the temperature of the engine oil and the temperature of the intake air are detected, and a range of economical fuel consumption is displayed in accordance with a result of the detection.
On the other hand, when the temperature of the engine is low, such as in the engine start period which is a state of a very low engine temperature where a sufficient engine warming characteristic is required, it is difficult to obtain sufficient engine power because the atomization of fuel is insufficient when the engine temperature is low, as compared with a state of a medium engine temperature, and the loss of the engine power increases due to the viscosity of the engine oil.
Therefore, if a reference level of the determination, such as an up-shift, for the indication of the shift operation for the manual transmission gear is selected to be the same for both of the low temperature range and the medium temperature range, driveability of the vehicle will be worsened in the low temperature range, and the warming-up of the engine will be delayed because the heat generated by the engine is little.